Federal mandates passed in 2009 require whole shell egg producers to take numerous precautions to help prevent Salmonella enterica serovar Enteritidis in egg laying flocks. The Food and Drug Administration (FDA) reports as many as 79,000 illnesses and 30 deaths could be prevented each year if such precautions are implemented. The FDA mandates require periodic Salmonella testing, cleaning and sanitizing of positive houses, and impose protocols for preventing the introduction and spread of bacteria, pest control, as well as protocols for workers and equipment. Additional record keeping requirements are also part of the mandates.
However, these mandates are not required if the eggs are subjected to a pasteurization process before they are sold to consumers. While several procedures using different techniques exist, such as microwave, radio wave, ozone, and basic convective heat treatments for pasteurizing whole shell eggs, only one of the methods is used commercially in the United States today. Although these decontamination processes vary significantly, all rely on heating the eggs, either fully or partially, to ensure proper reduction of the Salmonella population.
An example pasteurization process reveals some of the complications associated with methods that primarily use heat. The heat of the pasteurization process partially denatures egg proteins and changes the functionality of raw egg components. Lack of effective temperature monitoring and control increases the severity of these changes. Egg processors need to ensure that the thermal treatment is stringent enough to eliminate internal egg pathogens without causing thermal damage to egg components. Therefore, there is a need to accurately measure and promptly report internal egg temperature during the heating process. Current techniques to monitor an egg's internal temperature are cumbersome and often produce inconsistent results. Indirect methods of process control include regulating the temperature of a water bath in which the eggs are heated and regulating the time which the eggs spend in the bath. However, even these measurements are usually derived from those taken previously from the egg itself and are thus less than reliable.
Currently, the thermal processing of eggs is monitored using technologies developed for the canning industry. An example of this conventional temperature monitoring involves using thermocouples inserted inside the coldest spot of a number of test eggs, and locating the test eggs in the least-heated position in the apparatus heating the eggs, such as a water bath. Long wires transmit thermocouple signals from test eggs to signal reading devices and a data processing system located outside of the water bath. The data processing system amplifies the thermocouple signals, an analog-to-digital converter digitizes the signals, and computer software transforms the digitized signals to a temperature-time matrix.
Measuring internal egg temperature involves positioning a thermocouple in egg's coldest spot, which is an imprecise exercise. The egg shell is solid layer that is suitable for protecting potentially developing embryo. The shell keeps fluid parts in and extraneous substances out. Because the shell is made of a brittle porous material, inserting a temperature probe into the egg without cracking it is an art that takes time and many failures to master. Once inserted, the shell is not strong enough to reliably maintain the orientation of the probe or its position inside the egg. Therefore, a device is needed to hold the egg and temperature probe in the desired orientation and relative position. Consistency of probe orientation and position is also crucial. The center of the yolk heats much more slowly than the region at its boundary with the albumen just outside the yolk. Inconsistency of temperature probe position can produce errors that would adversely affect process lethality or product quality.
There is clearly a need for a device which can replace the use of actual eggs to monitor and control the internal temperature of eggs subjected to pasteurization processes.